20 But you have an anointing from the Holy One, and all of you know the truth. 21 I do not write to you because you do not know the truth, but because you do know it and because no lie comes from the truth. 22 Who is the liar? It is the man who denies that Jesus is the Christ. Such a man is the antichrist—he denies the Father and the Son. 23 No one who denies the Son has the Father; whoever acknowledges the Son has the Father also.
That's a good marking point to remember; when we start slicing and dicing doctrine, remember that the core is Jesus. One can still disagree on some doctrinal points and both agree on Jesus as Lord and Savior.
Yesterday, I was reading this piece where someone was taking John Piper to task for stating that it's a sin not to like the doctrine of election. If you're of a universalist bent, like the author seems to be, you'll be quick to disagree. However, even if you disagree with Piper on this one, you'd be hard-pressed to call him the Antichrist or a small-a antichrist (John likely had the latter in mind rather than the end-times ultimate Dr Evil).
Flipping the bile in a different direction, casting Rob Bell as an antichrist would be problematic based on John's take, since he seems to be professing Jesus as Lord even as he sees Him saving everyone eventually; strangely, he and Piper might agree that folks are elected, except that Bell thinks no one loses in that primary.
Edgy theology, yes. Antichrists.... not quite. Both have strong theologies that not everyone will agree with, but neither rises quite to the point where the a-word can be trotted out. Bell comes close to meeting another a-word, apostate, as he resembles Unitarian Universalists as much as he resembles traditional evangelical thought, but doesn't quite deserve the bile he got a year ago when Love Wins came out.